In photosystem ii, as high-energy electrons are passed to the electron transport chain the chlorophyll gains new electrons from a. oxygen atoms b. water molecules c. hydrogen ions d. carbon dioxide

b. Water molecules

When sunlight is absorbed by one of many pigments present in photosystem II the light energy is distributed from pigment to pigment until it reaches the reaction center of photosystem II. The electrons present in the reaction center jumps to higher energy state on receiving light energy. Each high energy electron is passed to an acceptor molecule (plastoquinone) and replaced with an electron produced by splitting of water. The splitting of water produces oxygen and electrons. The high energy electrons are transferred to electron transport chain. The energy present in these electrons creates a gradient in the thylakoid membrane of chloroplast. The gradient facilitates the flow of H⁺ ions across thylakoid membrane and which lead to the production of ATP by enzyme ATP synthase.

Therefore, water is required to produce electrons in photosystem II.

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after a the power stroke, adp is released, but the cross-bridge formed is still in place. atp then binds to myosin, moving the myosin to its high-energy state, releasing the myosin head from the actin active site.